Cold-gas refrigerator, displacer seal to reduce frozen contaminants

ABSTRACT

A cold-gas machine includes first and second pistons for varying the volumes of a cold and a warm space; the first piston has a seal and a duct which communicates with a buffer space, the latter communicating via a duct with the warm space, debouching at a place situated between the axial boundaries of said seal. A non-return valve opens in the direction of the warm space is incorporated in this duct.

United States Patent Prast et al. 1 Sept. 5, 1972 [54] COLD-GAS REFRIGERATOR, [56] References Cited 32 3??? :Eghfgfig UNITED STATES PATENTS Inventors: Gfisben hast; Hendrik Jan Raw 2,982,088 5/1961 lneljer ..62/6 werdink both of Emmasingel, 3,145,629 8/1964 Gottzmann ..62/6 X Netherlands 3,303,658 2/1967 Chellis ..62/6 3,355,882 12/1967 Kohler ..62/6 [73] Assignee: U.S. Philips Corporation, New

York Primary Examiner-William J. Wye [22] Filed: Dec. 22, 1970 Attorney-Frank R. Trifari 0 ,6 2 [211 App! NO 1 0 6 57 ABSTRACT [30] Foreign Application Priority Dam A cold-gas machine includes first and second pistons for varying the volumes of a cold and a warm space; Jan. 2, 1970 Netherlands ..7000001 the first iston has a Seal and a duct which commu P nicates with a buffer space, the latter communicating CCll via a duct with the warm Space, debouching at a place [58] Fie'ld 62/6 situated between the axial boundaries of said seal. A nomretum valve Opens in the direction of the warm space is incorporated in this duct.

8 Claims, 4 Drawing Figures PATENTEBSEF 5 I972 SHEET 1 BF 2 HENDRIK J. RAUWERDINK AGENT PATENTED 5 I97? SHEEI 2 OF 2 INVENTORS GIJSBERT PRAST HENDRIK J. RAUWERDINK AGFNT COLD-GAS REFRIGERATOR, DISPLACER SEAL TO REDUCE FROZEN CONTAMINANTS BACKGROUND OF THE INVENTION The invention relates to a cold-gas machine, in particular a cold-gas refrigerator, comprising at least one cylinder having two pistons reciprocating therein for varying the volumes of a space having, in operation, a higher average temperature, and at least one space having, in operation, a lower average temperature. These spaces communicate with each other via a heat exchanger, preferably a regenerator, and at least the piston, which varies the volume of the lower tempera ture space further comprising a seal.

Cold-gas machines of the type to which the present invention relates are known and are formed by cold-gas engines and cold-gas refrigerators. In these machines the piston members move in such manner, that in the case of a cold-gas refrigerator, a working medium is compressed at a higher temperature when it is mainly in the higher temperature compression space, is then transported, via the regenerator in which the working medium cools, to an expansion space which is at a lower temperature, and expanded when it is mainly in said expansion space.

In cold-gas engines, compression takes place when the medium is mainly in the space which is at a lower temperature, while the expansion takes place when the medium is mainly in the space which is at a higher temperature. Machines of the present type may be constructed as machines of the displacer type or as machines of the two-piston type.

In order to check loss of cold from the space which is at the lower temperature, the piston which bounds said space is usually formed by a base portion which, on its side facing said space comprises, an insulating cap. In order to keep the detrimental influences of the gap between the insulating cap and the surrounding cylinder small, the gap width is chosen to be small. Furthermore, in order to check flow of medium through this gap, the base portion of the relative piston comprises a seal. This seal may be formed, for example, by a ribbon of a synthetic resin secured to the base portion. Other seals, for example, piston rings or O-rings, may also be used. However, this sea] never is complete, so that some reciprocating flow of medium in the gap between the cylinder and the piston-like member can always occur.

It has been found that during the flow to the expansion space any contaminations present in the medium are frozen-out in the gap and deposited on the gap walls. When the medium flows in the opposite direction, the deposited contaminations are not taken along. So an accumulation of contaminations in the gap takes place. As a result of this the cold production of the refrigerator and the power supplied by the cold-gas engine, respectively, decreases in course of time. This effect is extremely disadvantageous in particular in smaller cold-gas refrigerators operating in the vicinity of their lowest achievable temperature.

It is to be noted that US. Pat. No. 3,303,658 describes a refrigerator machine of the type in which a displacer, movable in a cylinder, separates a cold space from a warm space, which spaces communicate with each other through a regenerator; also the warm space is made to communicate alternately with an inlet for high-pressure medium and an outlet for low-pressure medium. The seal of the gap between the displacer and the cylinder in this type of machine is formed by two 0- rings; in order to prevent pollution of the gap, the space between the two O-rings is in constant open communication with the outlet in which a low pressure prevails.

SUMMARY OF THE NEW INVENTION It is the object of the invention to check pollution of the gap between the cylinder and the piston in a simple manner, and also in cold-gas refrigerators of the type mentioned in the preamble in which, in contrast with the known machine, the working medium flows through a closed cycle.

In order to realize this end, the cold-gas machine according to the invention is characterized in that at a location between the axial boundaries of the seal on the wall of the cylinder or relative piston, a duct debouches which communicates with a buffer space which communicates, via a duct, with the space having, in operation, the higher average temperature and in which duct a non-return valve is incorporated which opens in the direction of said space.

Since the buffer space communicates, via non-return valve, with the space having the higher average temperature, the valve will open as soon as the pressure therein becomes higher than that in the last-mentioned space, and the buffer space will empty in said higher temperature space. When the pressure in the compression and expansion spaces becomes higher than that in the buffer space, medium will flow to the buffer space along the seal. In this very simple manner and without supply or exhaust to or from outside the machine being necessary, one can prevent medium flow from the warmer space into the part of the gap which is at a low temperature. Thus, substantially no deposit of contaminations in the gap will take place, so that the machine will still provide its optimum output also after a longer period of operation.

In order to restrict the deposition of contaminations even more drastically, a further favorable embodiment of the cold-gas machine according to the invention comprises another non-return valve in the duct debouching on the wall of the cylinder or piston, which valve opens in the direction of the buffer space.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to two constructions of cold-gas machines which are constructed as cold-gas refrigerators and which are shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 diagrammatically shows a cold-gas refrigerator of the displacer type,

FIGS. 2 and 3 show two other constructions of the displacer seal used in FIG. 1,

FIG. 4 diagrammatically shows a cold-gas refrigerator of the two-piston type.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1 in FIG. 1 denotes a cylinder. A piston 2 and a displacer 3 which are connected to a driving mechanism (not shown) by a piston rod 4 and a displacer rod 5, respectively, reciprocate in said the cylinder. The displacer 3 consists of a base portion 6, a part '7 in which a regenerator 8 is incorporated and an insulating cap 9. Between the displacer and the piston a compression space 10 is present in which a cooler l I is accommodated. The compression space 10 communicates with the expansion space via ducts 12 in the base portion 6 of the displacer, the regenerator 8, bores 13in the wall of the displacer part 7 and gap 14.

The gap 14 continues downwards up to base portion 6 which comprises a ribbon 16 of a synthetic resin which ensures the seal between the portion 6 and the cylinder 1. The base portion 6 furthermore comprises an annular groove 17, with which a duct 18 communicates, which communicates with a buffer space 19. The buffer space 19 communicates, via a duct 20, with the compression space 10. A non-return valve 21 which opens in the direction of the compression space is incorporated in the duct 20.

The operation of the refrigerator may be assumed to be known. When the displacer 3 is moved, transport of medium takes place from the compression space 10 to the expansion space 15, and conversely. The medium flows for the greater part through ducts I2, regenerator 8 and gap 14. However, the possibility exists that some medium passes the seal 16. When medium flows to the compression space this presents no difficulties. When on the contrary medium flows from the compression space along the seal 16 into the gap 14, contaminations present in the medium will freeze out on the cold walls of the gap, which in the long run will give rise to a decrease of the cold production.

In order to prevent this, the groove 17, duct 18, buffer space 19 and duct 26 have been incorporated. When the pressure in the buffer space 19 is lower than in the compression and expansion spaces, medium from gap 14 and from compression space 10 can flow to the buffer space 19 via seal 16. If, however, the pressure in the space 19 becomes higher then that in the compression space 10, the valve 21 will open after which medium flows from the buffer space 19 via duct to the compression space 10. Of course, the pressure in groove 17 at that instant will also be higher than that in the gap 14 and compression space 20, so that the possibility exists that a small flow of medium also occurs to gap 14 and compression space 10 along the seal. However, this flow will only be small so that the quantity of contaminations occurring in gap 14 will only be small and will not give rise to difficulties. By suitable choice of the volume of the buffer space 19 it is possible to avoid this return flow of medium along the seal substantially entirely. In this manner it is prevented in a very simple manner and while maintaining the closed medium circuit, that contaminations deposit in the gap 14.

FIG. 2 diagrammatically shows how the groove 17, duct 1.8, buffer space 19 and duct 20 are arranged outside the displacer instead of in the displacer.

FIG. 3 shows an embodiment which in general corresponds to that shown in FIGS. 1 and 2, but in which a further non-return valve is incorporated in duct 18 and opens in the direction of the buffer space 19. The result of this is that when the pressure in the buffer space 19 becomes higher than in the compression and expansion spaces, non-return valve 23 will prevent return flow of medium via seal 16 to gap 14 and compression space 10, respectively, so that all the medium flows to the compression space 10 via duct 20. As a result of this also, deposits of contaminations in the gap [4 are prevented. Although the measure according to the invention has been described with reference to a refrigerator in which the regenerator is incorporated in the displacer, it will be obvious that the relative measure can be applied with the same advantages to coldgas refrigerators, in which the regenerator is arranged outside the cylinder,

FIG. 4 diagrammatically shows a cold-gas refrigerator of the two-piston type. In this embodiment two pistons 42 and 43 which are connected to a driving mechanism (not shown) via piston rods 44 and 45 are incorporated in a cylinder. The piston 42 bounds with its one end a compression space 46 which, via a cooler 47, regenerator 48 and a freezer 49, communicates with an expansion space 50 which is at a low tempera ture. The piston 43 is constructed from a base portion 51 and an insulating cap 52. In the working space constituted by compression space 46 and expansion space 50 plus the intermediately iocated connection, working medium under a given average pressure is present. Behind the piston 42 and 43, buffer spaces 53 and 54 are present which are at such an average pressure that the forces acting on the piston are compensated.

The base portion 51 of the piston 43 comprises a seal 55. In order to prevent flow of medium to the gap 56 between the cap 52 and the cylinder 41, the cylinder wall comprises a groove 57 which communicates with the compression space 46 via duct 58, buffer space 59 and duct 60 having a non-return valve 61 incorporated therein. In this manner, as also in the constructions according to the preceding figures, one can prevent the deposit of contaminations in the gap 56.

What is claimed is:

1. In a cold-gas refrigerator including a piston and a displacer reciprocally movable within the bore of a cylinder for defining variable volume compression and expansion spaces for operation at relatively higher and lower temperatures respectively, said spaces being in communication with each other via a regenerator situated between them, said displacer having axially spaced base and displacer portions, the base portion having an outer surface adjacent the cyiinders bore with an annular space defined between said outer surface and said bore, the displacer portion having an outer surface adjacent the cylinders bore with an annular gap defined therebetween, and seal means in said annular space for axially separating said gap and expansion space from said compression space, the improvement in combination therewith comprising means for reducing the formation of frozen contaminants in said gap and surfaces defining said gap, the displacer defining therein a buffer space with a first duct communicating said buffer space with said annular space, and a second duct communicating said buffer space with said compression space, said means for reducing contaminants further comprising a one-way valve situated in said second duct and opening only toward said compression space and a second one-way valve situated in said first duct and opening only toward said buffer space.

2. In a cold-gas refrigerator including a piston and a displacer reciprocally movable within the bore of a cylinder for defining variable volume compression and expansion spaces for operation at relatively higher and lower temperature respectively, said spaces being in communication with each other through a regenerator, said displacer having axially spaced base and displacer portions, the base portion having an outer surface adjacent the cylinders bore with an annular space defined therebetween, the displacer portion having an outer surface adjacent the cylinders bore with an annular gap defined therebetween, and seal means in said annular space for axially separating said gap and expansion space from said compression space, the improvement in combination therewith comprising means for reducing the formation of frozen contaminants in said gap and surfaces defining said gap, the displacer defining therein a buffer space with a first duct communicating said buffer space with said annular space, and a second duct communicating said buffer space with said compression space, said means for reducing contaminants further comprising a one-way valve situated in said second duct and opening only toward said compression space.

3. In a cold-gas refrigerator including a piston and a displacer reciprocally movable within the bore of a cylinder for defining variable volume compression and expansion spaces for operation at relatively higher and lower temperature respectively, said spaces being in communication with each other through a regenerator, said displacer having axially spaced base and displacer portions, the base portion having an outer surface adjacent the cylinder's bore with an annular space defined therebetween the displacer portion having an outer surface adjacent the cylinders bore with an annular gap defined therebetween, and seal means in said annular space for axially separating said gap and expansion space from said compression space, the improvement in combination therewith of means for reducing the formation of frozen contaminants in said gap and surfaces defining said gap, comprising duct means external of said cylinder communicating said compression, higher-temperature space with said annular space, a buffer space being defined in said duct, and a oneway valve situated in the duct means intermediate the compression space and buffer space and opening only toward the compression space.

4. Apparatus according to claim 3 further comprising a second one-way valve situated in said duct means intermediate said buffer space and said annular space, and opening only toward the buffer space.

5. Apparatus according to claim 2 wherein said regenerator is carried by said displacer.

6. Apparatus according to claim 1 wherein said regenerator is carried by said displacer.

7. Apparatus according to claim 2 wherein said regenerator is situated fixedly in the cylinder bore between the piston and displacer.

8. Apparatus according to claim 1 wherein said regenerator is situated fixedly in the cylinder bore between the piston and dispenser. 

1. In a cold-gas refrigerator including a piston and a displacer reciprocally movable within the bore of a cylinder for defining variable volume compression and expansion spaces for operation at relatively higher and lower temperatures respectively, said spaces being in communication with each other via a regenerator situated between them, said displacer having axially spaced base and displacer portions, the base portion having an outer surface adjacent the cylinder''s bore with an annular space defined between said outer surface and said bore, the displacer portion having an outer surface adjacent the cylinder''s bore with an annular gap defined therebetween, and seal means in said annular space for axially separating said gap and expansion space from said compression space, the improvement in combination therewith comprising means for reducing the formation of frozen contaminants in said gap and surfaces defining said gap, the displacer defining therein a buffer space with a first duct communicating said buffer space with said annular space, and a second duct communicating said buffer space with said compression space, said means for reducing contaminants further comprising a one-way valve situated in said second duct and opening only toward said compression space and a second one-way valve situated in said first duct and opening only toward said buffer space.
 2. In a cold-gas refrigerator including a piston and a displacer reciprocally movable within the bore of a cylinder for defining variable volume compression and expansion spaces for operation at relatively higher and lower temperature respectively, said spaces being in communication with each other through a regenerator, said displacer having axially spaced base and displacer portions, the base portion having an outer surface adjacent the cylinder''s bore with an annular space defined therebetween, the displacer portion having an outer surface adjacent the cylinder''s bore with an annular gap defined therebetween, and seal means in said annular space for axially separating said gap and expansion space from said compression space, the improvement in combination therewith comprising means for reducing the formation of frozen contaminants in said gap and surfaces defining said gap, the displacer defining therein a buffer space with a first duct communicating said buffer space with said annular space, and a second duct communicating said buffer space with said compression space, said means for reducing contaminants further comprising a one-way valve situated in said second duct and opening only toward said compression space.
 3. In a cold-gas refrigerator including a piston and a displacer reciprocally movable within the bore of a cylinder for defining variable volume compression and expansion spaces for operation at relatively higher and lower temperature respectively, said spaces being in communication with each other through a regenerator, said displacer having axially spaced base and displacer portions, the base portion having an outer surface adjacent the cylinder''s bore with an annular space defined therebetween the displacer portion having an outer surface adjacent the cylinder''s bore with an annular gap defined therebetween, and seal means in said annular space for axially separating said gap and expansion space from said compression space, the improvement in combination therewith of means for reducing the formation of frozen contaminants in said gap and surfaces defining said gap, comprising duct means external of said cylinder communicating said compression, higher-temperature space with said annular space, a buffer space being defined in said duct, and a one-way valve situated in the duct means intermediate the compression space and buffer space and opening only toward the compression space.
 4. Apparatus according to claim 3 further comprising a second one-way valve situated in said duct means intermediate said buffer space and said annular space, and opening only toward the buffer space.
 5. Apparatus according to claim 2 wherein said regenerator is carried by said displacer.
 6. Apparatus according to claim 1 wherein said regenerator is carried by said displacer.
 7. Apparatus according to claim 2 wherein said regenerator is situated fixedly in the cylinder bore between the piston and displacer.
 8. Apparatus according to claim 1 wherein said regenerator is situated fixedly in the cylinder bore between the piston and dispenser. 